@article{sprouse_lund_miller_mclaughlin_mumpower_2024, title={Emergent Nucleosynthesis from a 1.2 s Long Simulation of a Black Hole Accretion Disk}, volume={962}, ISSN={["1538-4357"]}, url={https://doi.org/10.3847/1538-4357/ad1819}, DOI={10.3847/1538-4357/ad1819}, abstractNote={
 We simulate a black hole accretion disk system with full-transport general relativistic neutrino radiation magnetohydrodynamics for 1.2 s. This system is likely to form after the merger of two compact objects and is thought to be a robust site of r-process nucleosynthesis. We consider the case of a black hole accretion disk arising from the merger of two neutron stars. Our simulation time coincides with the nucleosynthesis timescale of the r-process (∼1 s). Because these simulations are time-consuming, it is common practice to run for a “short” duration of approximately 0.1–0.3 s. We analyze the nucleosynthetic outflow from this system and compare the results of stopping at 0.12 and 1.2 s. We find that the addition of mass ejected in the longer simulation as well as more favorable thermodynamic conditions from emergent viscous ejecta greatly impacts the nucleosynthetic outcome. We quantify the error in nucleosynthetic outcomes between short and long cuts.}, number={1}, journal={ASTROPHYSICAL JOURNAL}, author={Sprouse, Trevor M. and Lund, Kelsey A. and Miller, Jonah M. and Mclaughlin, Gail C. and Mumpower, Matthew R.}, year={2024}, month={Feb} }
 @article{lund_mclaughlin_miller_mumpower_2024, title={Magnetic Field Strength Effects on Nucleosynthesis from Neutron Star Merger Outflows}, volume={964}, ISSN={["1538-4357"]}, url={https://doi.org/10.3847/1538-4357/ad25ef}, DOI={10.3847/1538-4357/ad25ef}, abstractNote={
 Magnetohydrodynamic turbulence drives the central engine of post-merger remnants, potentially powering both a nucleosynthetically active disk wind and the relativistic jet behind a short gamma-ray burst. We explore the impact of the magnetic field on this engine by simulating three post-merger black hole accretion disks using general relativistic magnetohydrodynamics with Monte Carlo neutrino transport, in each case varying the initial magnetic field strength. We find increasing ejecta masses associated with increasing magnetic field strength. We find that a fairly robust main r-process pattern is produced in all three cases, scaled by the ejected mass. Changing the initial magnetic field strength has a considerable effect on the geometry of the outflow and hints at complex central engine dynamics influencing lanthanide outflows. We find that actinide production is especially sensitive to magnetic field strength, with the overall actinide mass fraction calculated at 1 Gyr post-merger increasing by more than a factor of 6 with a tenfold increase in magnetic field strength. This hints at a possible connection to the variability in actinide enhancements exhibited by metal-poor, r-process-enhanced stars.}, number={2}, journal={ASTROPHYSICAL JOURNAL}, author={Lund, Kelsey A. and Mclaughlin, Gail C. and Miller, Jonah M. and Mumpower, Matthew R.}, year={2024}, month={Apr} }
 @article{holmbeck_barnes_lund_sprouse_mclaughlin_mumpower_2023, title={Superheavy Elements in Kilonovae}, volume={951}, ISSN={["2041-8213"]}, url={https://doi.org/10.3847/2041-8213/acd9cb}, DOI={10.3847/2041-8213/acd9cb}, abstractNote={As LIGO-Virgo-KAGRA enters its fourth observing run, a new opportunity to search for electromagnetic counterparts of compact object mergers will also begin. The light curves and spectra from the first “kilonova” associated with a binary neutron star merger (NSM) suggests that these sites are hosts of the rapid neutron capture (“r”) process. However, it is unknown just how robust elemental production can be in mergers. Identifying signposts of the production of particular nuclei is critical for fully understanding merger-driven heavy-element synthesis. In this study, we investigate the properties of very neutron-rich nuclei for which superheavy elements (Z ≥ 104) can be produced in NSMs and whether they can similarly imprint a unique signature on kilonova light-curve evolution. A superheavy-element signature in kilonovae represents a route to establishing a lower limit on heavy-element production in NSMs as well as possibly being the first evidence of superheavy-element synthesis in nature. Favorable NSM conditions yield a mass fraction of superheavy elements X Z≥104 ≈ 3 × 10−2 at 7.5 hr post-merger. With this mass fraction of superheavy elements, we find that the component of kilonova light curves possibly containing superheavy elements may appear similar to those arising from lanthanide-poor ejecta. Therefore, photometric characterizations of superheavy-element rich kilonova may possibly misidentify them as lanthanide-poor events.}, number={1}, journal={ASTROPHYSICAL JOURNAL LETTERS}, author={Holmbeck, Erika M. and Barnes, Jennifer and Lund, Kelsey A. and Sprouse, Trevor M. and McLaughlin, G. C. and Mumpower, Matthew R.}, year={2023}, month={Jul} }
 @article{lund_engel_mclaughlin_mumpower_ney_surman_2023, title={The Influence of beta-decay Rates on r-process Observables}, volume={944}, ISSN={["1538-4357"]}, url={https://doi.org/10.3847/1538-4357/acaf56}, DOI={10.3847/1538-4357/acaf56}, abstractNote={The rapid neutron capture process (r-process) is one of the main mechanisms whereby elements heavier than iron are synthesized, and is entirely responsible for the natural production of the actinides. Kilonova emissions are modeled as being largely powered by the radioactive decay of species synthesized via the r-process. Given that the r-process occurs far from nuclear stability, unmeasured beta-decay rates play an essential role in setting the timescale for the r-process. In an effort to better understand the sensitivity of kilonova modeling to different theoretical global beta-decay descriptions, we incorporate these into nucleosynthesis calculations. We compare the results of these calculations and highlight differences in kilonova nuclear energy generation and light-curve predictions, as well as final abundances and their implications for nuclear cosmochronometry. We investigate scenarios where differences in beta-decay rates are responsible for increased nuclear heating on timescales of days that propagates into a significantly increased average bolometric luminosity between 1 and 10 days post-merger. We identify key nuclei, both measured and unmeasured, whose decay rates directly impact nuclear heating generation on timescales responsible for light-curve evolution. We also find that uncertainties in beta-decay rates significantly impact age estimates from cosmochronometry.}, number={2}, journal={ASTROPHYSICAL JOURNAL}, author={Lund, Kelsey A. and Engel, J. and McLaughlin, G. C. and Mumpower, M. R. and Ney, E. M. and Surman, R.}, year={2023}, month={Feb} }
 @book{lund_miller_mumpower_mclaughlin_2022, title={Magnetic Turbulence in Post-Merger Accretion Disks}, url={https://doi.org/10.2172/1870625}, DOI={10.2172/1870625}, abstractNote={in the absence of a magnetic field and are most pronounced in systems with secondary-to-primary mass ratios larger than 0.6. We further analyze carbon burning in these systems to assess the possibility of detonation. Unlike the case of a 1.1+1.0 M{sub ⊙} C/O WD binary, we find that WD binary systems with lower mass and smaller mass ratios do not detonate as SNe Ia up to ∼8–22 outer dynamical times. Two additional models do, however, undergo net heating, and their secular increase in temperature could possibly result in a detonation on timescales longer than those considered here.}, author={Lund, Kelsey and Miller, Jonah and Mumpower, Matthew and McLaughlin, Gail}, year={2022}, month={May} }
 @article{barnes_zhu_lund_sprouse_vassh_mclaughlin_mumpower_surman_2021, title={Kilonovae Across the Nuclear Physics Landscape: The Impact of Nuclear Physics Uncertainties on r-process-powered Emission}, volume={918}, ISSN={["1538-4357"]}, url={https://doi.org/10.3847/1538-4357/ac0aec}, DOI={10.3847/1538-4357/ac0aec}, abstractNote={Merging neutron stars produce “kilonovae”—electromagnetic transients powered by the decay of unstable nuclei synthesized via rapid neutron capture (the r-process) in material that is gravitationally unbound during inspiral and coalescence. Kilonova emission, if accurately interpreted, can be used to characterize the masses and compositions of merger-driven outflows, helping to resolve a long-standing debate about the origins of r-process material in the Universe. We explore how the uncertain properties of nuclei involved in the r-process complicate the inference of outflow properties from kilonova observations. Using r-process simulations, we show how nuclear physics uncertainties impact predictions of radioactive heating and element synthesis. For a set of models that span a large range in both predicted heating and final abundances, we carry out detailed numerical calculations of decay product thermalization and radiation transport in a kilonova ejecta with a fixed mass and density profile. The light curves associated with our models exhibit great diversity in their luminosities, with peak brightness varying by more than an order of magnitude. We also find variability in the shape of the kilonova light curves and their color, which in some cases runs counter to the expectation that increasing levels of lanthanide and/or actinide enrichment will be correlated with longer, dimmer, redder emission.}, number={2}, journal={ASTROPHYSICAL JOURNAL}, author={Barnes, Jennifer and Zhu, Y. L. and Lund, K. A. and Sprouse, T. M. and Vassh, N. and McLaughlin, G. C. and Mumpower, M. R. and Surman, R.}, year={2021}, month={Sep} }
 @article{zhu_lund_barnes_sprouse_vassh_mclaughlin_mumpower_surman_2021, title={Modeling Kilonova Light Curves: Dependence on Nuclear Inputs}, volume={906}, ISSN={["1538-4357"]}, url={https://doi.org/10.3847/1538-4357/abc69e}, DOI={10.3847/1538-4357/abc69e}, abstractNote={The mergers of binary neutron stars, as well as black hole–neutron star systems, are expected to produce an electromagnetic counterpart that can be analyzed to infer the element synthesis that occurred in these events. We investigate one source of uncertainties pertinent to lanthanide-rich outflows: the nuclear inputs to rapid neutron capture nucleosynthesis calculations. We begin by examining 32 different combinations of nuclear inputs: eight mass models, two types of spontaneous fission rates, and two types of fission daughter product distributions. We find that such nuclear physics uncertainties typically generate at least one order of magnitude uncertainty in key quantities such as the nuclear heating (one and a half orders of magnitude at 1 day post-merger), the bolometric luminosity (one order of magnitude at 5 days post-merger), and the inferred mass of material from the bolometric luminosity (factor of 8 when considering the 8–10 day region). Since particular nuclear processes are critical for determining the electromagnetic signal, we provide tables of key nuclei undergoing β-decay, α-decay, and spontaneous fission important for heating at different times, identifying decays that are common among the many nuclear input combinations.}, number={2}, journal={ASTROPHYSICAL JOURNAL}, publisher={American Astronomical Society}, author={Zhu, Y. L. and Lund, K. A. and Barnes, J. and Sprouse, T. M. and Vassh, N. and McLaughlin, G. C. and Mumpower, M. R. and Surman, R.}, year={2021}, month={Jan} }
 @article{kilonovae across the nuclear physics landscape: the impact of nuclear physics uncertainties on r-process-powered emission_2020, year={2020}, month={Oct} }